Preservative-free ophthalmic pharmaceutical formulation

A method of manufacturing a sterile, preservative free ophthalmic formulation solution without steam sterilization or autoclaving comprising:

• a) heating a first mixture comprising a first solution that consists essentially of hydroxyethyl cellulose dissolved in water and is devoid of any preservative to a temperature of about 94° C. to about 97° C. for a sufficient time to produce a second mixture comprising a second solution having viscosity of about 100±10 centipoise and devoid of any preservative;
• b) dissolving a carbonic anhydrase inhibitor in the second mixture to produce a third mixture comprising a third solution that is devoid of any preservative, wherein the carbonic anhydrase inhibitor comprises dorzolainide, or a salt thereof;
• c) adjusting pH of the third mixture to between 5.5 to 6.0 to produce a fourth mixture comprising a fourth solution that is devoid of any preservative and heating the fourth mixture to between 43° C. to 47° C.;
• and
• d) sterilizing the fourth mixture by aseptic filtration which comprises filtration through a sterilization filter having a pore size of about 0.2 microns to produce a fifth mixture which is a sterile, preservative free ophthalmic formulation solution that is devoid of any preservative and that is produced without steam sterilization or autoclaving.